This invention relates to implantable prostheses and tissue expanders, and more particularly to implantable mammary prostheses and soft tissue expanders.
Implantable prostheses are commonly used to replace or augment body tissue. In the case of the female breast, it sometimes necessary to remove some or all of the mammary gland and surrounding tissue in order to treat breast cancer. This surgery leaves a void that can be filled with an implantable prosthesis. The implant serves to support surrounding tissue and to maintain the appearance of the body. The restoration of the normal appearance of the body has an extremely beneficial psychological effect on post-operative patients, eliminating much of the shock and depression that often follows extensive surgical procedures. Implantable mammary prostheses are also used more generally for enlargement of the breast.
Implantable mammary prostheses are commonly formed of a silicone polymer shell and are filled with saline or some other fluid or gel.
Implantable mammary prostheses generally have a relatively flat posterior face that is placed against the patient""s chest and a domed anterior face. It is often desirable for the region where the anterior face meets the posterior face, the perimeter region, to have a relatively small radius of curvature, particularly at the upper pole of the prosthesis, i.e., the portion of the prosthesis that is uppermost when the patient is standing. A relatively narrow radius of curvature in the transition between the anterior face and the posterior face in the upper pole of the prosthesis is desirable because it permits a relatively smooth transition between the mammary tissue and the implant when the prosthesis is implanted. However, a small radius is sometimes associated with the appearance of creases that extend inward from the perimeter of the prosthesis in the region of relatively small radius. This is sometimes referred to as a scalloping effect. Scalloping tend to occur when the prosthesis is filled with fluid and the patient is upright such that the weight of the filling material is pulling downward on the prosthesis. The creases often appear on the anterior face of the prosthesis. This is aesthetically undesirable as the creases can sometimes be discerned through the overlying skin of the patient.
The prosthesis of the invention are configured such that the average thickness of the shell in the region where the posterior and anterior faces meet is greater, e.g., at least twice, the thickness of the shell in the region of the anterior face. Applicants have found that this reinforcement can reduce or eliminate undesirable scalloping effects. In some embodiments, the average thickness of the shell in the region of posterior face is also greater, e.g., at least twice, the thickness of the shell in the region of the anterior face. Moreover, because the reinforcement is preferably confined to the perimeter (or radius) of the shell and, optionally, posterior face of the shell, it is possible for nearly the entire anterior face of the prosthesis to be formed of relatively thin material. This preserves a natural appearance of the prosthesis when it is implanted.
The invention features an implantable prosthesis comprising an elastomeric shell having an anterior face, a posterior face, and a perimeter region where the anterior face and the posterior face meet, wherein the average thickness of the shell in at least a reinforced portion of the perimeter region is greater than the average thickness of the shell in the anterior face. In various preferred embodiments, the prosthesis is a mammary prosthesis, the average thickness of the shell in the reinforced portion of the perimeter region is about 0.02 to 0.08 inches, the average thickness of the shell in the entire perimeter region is greater than the average thickness of the shell in the anterior face, the average thickness of the posterior face of the shell is about 0.02 to 0.08 inches, the average thickness of the anterior face of the shell is less than about 0.04 inches, the average thickness of the anterior face of the shell is less than about 0.03 inches, the prosthesis includes a filling port, and the prosthesis is filled with a gel or a liquid.
The invention also features a kit comprising a prosthesis of the invention and a means for filling the prosthesis with a liquid or a gel. In a preferred embodiment, the filling means comprises a syringe and a tube adapted to connect the syringe to the filling port of the shell of the prosthesis.
The invention further features a method for forming a prosthesis, the method comprising: (a) providing a mandrel adapted for dip molding a mammary prosthesis, the mandrel having an anterior face, a posterior face and a perimeter region where the anterior face and the posterior face meet; (b) masking both the anterior face and the posterior face of the mandrel while leaving at least a portion of the perimeter region free of masking; (c) dipping the masked mandrel into a silicone dispersion at least one time; (d) removing the mandrel from the silicone dispersion; (e) removing the masking from the mandrel; and (f) dipping the unmasked mandrel into a silicone dispersion at least one time.
The invention also features a method for forming a prosthesis, the method comprising: (a) providing a mandrel adapted for dip molding a mammary prosthesis, the mandrel having an anterior face, a posterior face and a perimeter region where the anterior face and the posterior face meet; (b) masking the anterior face of the mandrel while leaving at least a portion of the perimeter region and the posterior face free of masking; (c) dipping the masked mandrel into a silicone dispersion at least one time; (d) removing the mandrel from the silicone dispersion; (e) removing the masking from the mandrel; and (f) dipping the unmasked mandrel into a silicone dispersion at least one time. In various embodiments, the masked mandrel is dipped into a silicone dispersion at least two times; and the unmasked mandrel is dipped into a silicone dispersion at least two times. In other embodiment a first portion of the masking is removed, the mandrel is dipped at least once, the remainder of the masking is removed and the mandrel is dipped again.
The invention also features a method for forming a prosthesis shell, the comprising: (a) dipping an appropriately sized and shaped mandrel into a silicone dispersion such that the posterior face and perimeter of the mandrel, but not the entire anterior face of the mandrel is submerged in the dispersion; (b) repeating step (a) until a desired partial thickness is achieved; (c) dipping the entire mandrel into the dispersion; and (d) repeating step (c) until a desired final thickness is achieved.
The invention also features a method for forming a reinforced mammary prosthesis, the method comprising: (a) forming an elastomeric mammary prosthesis shell, the shell having an inner surface, an outer surface, anterior face, a posterior face, and a perimeter region where the anterior face and the posterior face meet; and (b) adhering a sheet a of elastomeric material to the inner surface of the shell at the perimeter region.
The details of one or more embodiments of the invention are set forth in the accompanying drawings and the description below. Other features, objects, and advantages of the invention will be apparent from the description and drawings, and from the claims.